1. Field of the Invention
The subject of the present invention is an electric arc furnace for the production of steel, as well as a method for operating this furnace.
2. Description of the Related Art
As is known, steel is obtained in such furnaces by melting scrap between electrodes, these furnaces comprising gas injectors provided with respective cooling chambers placed in a wall of the furnace. These injectors make it possible for oxygen and natural gas to be injected simultaneously so as to increase the energy supplied to the metal.
The use of burners and of injectors consisting of lances with oxygen injected at supersonic speed is well known. In the technology of manufacturing steel in an electric arc furnace, scrap is melted by establishing, in particular, an electric arc between the electrodes of the furnace and the metal so as to supply energy, melt the metal and keep it molten. By using burners and by adding oxygen and carbon, the additional energy that speeds up the metal melting process can be delivered to the metal.
The fitting of oxygen and carbon injectors and of burners in the wall of the furnace cannot be accomplished without taking into account a number of parameters, namely the position of the injector or of the burner on the panel, the available space outside the furnace at the chosen place for fitting them, etc. Each wall injector or each burner is protected by a cooling chamber consisting of a water-cooled cooling box usually made of copper, which is inserted into the panel.
A burner makes it possible to melt the scrap more rapidly and to eliminate any cold spots in the furnace, while an oxygen lance makes it possible to inject oxygen into the slag in order to obtain a foaming slag and to inject oxygen into the pool in order to decarburize it. The angle of propagation of the burner flame in the vertical plane with respect to the horizontal plane must lie within a defined angular range, the flame not being able to be angled radially in the furnace. On the other hand, the angle of oxygen injection with respect to the surface of the pool must be relatively large so that the oxygen can penetrate the pool or the slag without bouncing back off the surface of either of them. In practice, the angles of oxygen injection in the vertical plane must be greater than 40 degrees with respect to the horizontal plane.
In order to reduce the volume requirement and the problems caused by the multiplicity of holes in the panels of the furnace, devices have been created for fulfilling several functions with the same gas outlets. Thus, burners are known which can be switched to "oxygen lance" mode or oxygen lances are known which can operate in "burner" mode using the same gas outlets.
These devices therefore propagate their flame and inject their oxygen in the same direction. They do not allow the angle of oxygen injection and that of propagation of the flame to be modified.